A user can generally determine whether a filmstrip disposed within a film cartridge has been exposed. For example, as illustrated in FIG. 1, a typical unexposed 35mm film product has a portion of a filmstrip 10 positioned outside of a film cartridge 12. Once the filmstrip has been exposed, the entire filmstrip is wound into the film cartridge; no portion of the filmstrip remains outside of the film cartridge. As such, a user is able to determine whether the filmstrip has been exposed.
However, for some photographic film products, such a visual inspection does not provide an indication of whether a filmstrip has been exposed. For example, for typical APS film product, no portion of the filmstrip is positioned outside of the film cartridge when the filmstrip is both unexposed and exposed. In contrast, for other types of film product, a portion of the filmstrip is positioned outside of the film cartridge when the filmstrip is both unexposed and exposed. Thus, a user is not able to determine the state (i.e., unexposed or exposed) of the filmstrip from the positioning of the filmstrip relative to the film cartridge.
Failure to recognize an exposed filmstrip can be detrimental since an exposed filmstrip may be re-exposed (i.e., double exposure). Conversely, failure to recognize an unexposed filmstrip may cause the unexposed filmstrip to be wasted by passage through a developing process without producing an image.
U.S. Pat. No. 5,032,862 (Behnke) discloses an indicator to indicate that a film cartridge has been used. Behnke teaches a film spool having a frangible indicator layer located to extend proximate the outer side of face of the end wall or canister end cap. The frangible indicator layer is penetrated by a plunger and punctured when the filmstrip is exposed.
U.S. Pat. No. 5,404,188 (Takahashi et al) discloses a film cartridge which is provided with a first indicating member which is to be broken in response to the loading of the film in a camera, and a second indicating member which is to be broken in response to a specific photographing method, such as panoramic photographing.
U.S. Pat. No. 4,682,870 (Atkinson), commonly assigned, relates to a particular type of camera requiring an exposed film to receive special handling by a photofinisher. A film spool includes a coaxial hole opening at one end of the spool and a readily fracturable element located within the coaxial hole.
While such apparatus may have achieved certain degrees of success in their particular applications, each apparatus requires the destruction of a component as an indication of film exposure. Such destruction can generate debris or other fragments which can interfere with the operation of the camera. Indeed, such debris can be detrimental to the operation of the camera or the exposure of the filmstrip.
Accordingly, a need continues to exist for an indicator to indicate that a filmstrip has been exposed wherein no destruction of a component is required, and no debris is generated.